Apple's own iCloud utility for Windows will add iCloud data to Outlook, but only as a secondary folder tree. CodeTwo cleans up the integration and brings all of your data together. The syncing works both ways (if you want it to), meaning that a new calendar appointment created within Outlook will automatically be pushed to your iOS devices without any extra hassle.

CodeTwo Sync for iCloud has a free 30 day trial, after which it will only sync calendars. The full version costs $10 and can be purchased from the developer's website.